The present invention relates to the field of optical fiber storage systems and, more particularly, to a device for separating portions of spooled optical fibers.
In a submarine optical transmission system, optical signals transmitted through the submarine optical fiber cable become attenuated over the length of the cable, which may stretch thousands of miles. To compensate for this signal attenuation, optical repeaters are strategically positioned along the length of the cable.
FIG. 1 illustrates a perspective view of a typical submarine optical repeater 10 having a cylindrical housing 12. A first submarine optical cable 16 enters repeater 10 at first end cover 14 and connects to first internal optical cable 18, which, in turn, connects to an optical repeater assembly 20. Optical repeater assembly 20 typically includes at least the following items (not shown in FIG. 1): optical components, connecting optical fibers, electronic circuits, and connecting wiring. Optical repeater assembly 20 connects via a second internal optical cable 19 to a second submarine optical cable 17, which exits repeater 10 at second end cover 15.
Typically, the optical fibers found within optical repeaters are circular in cross-section, and are constructed of glass surrounded by a protective jacket that is thicker than the glass. For example, a typical glass fiber (xe2x80x9cglass fiberxe2x80x9d, xe2x80x9cbare fiberxe2x80x9d, or xe2x80x9cunjacketed fiberxe2x80x9d) can have an outer diameter of approximately 0.010 inches, and a typical jacketed fiber can have an outer diameter of approximately 0.040 to 0.060 inches.
The glass fiber is fragile. Because even microscopic damage to the glass fiber can adversely affect the reliability of the optical repeater (and, as a result, the reliability of the entire submarine optical fiber cable system), great efforts are normally taken to protect the glass fiber from damage. Generally, the likelihood of damage to the glass fiber can be reduced by ensuring that any curvature in the glass fiber meets or exceeds the minimum bending radius of the glass fiber. However, the minimum bending radius of the glass fiber is a function of the expected life of the glass fiber. For example, when at least a 25-year life is expected, the glass fiber typically has a minimum bending radius of approximately 1 inch. This is referred to as the reliability-adjusted minimum bending radius of the glass fiber, because meeting or exceeding this value provides acceptable reliability from bending damage during the expected life of the glass fiber.
Typically, the optical components found within optical repeaters are manufactured with a segment of optical fiber attached at each end and cut to a specified length. Each fiber segment contains a jacketed portion of specified length located adjacent to the optical component, and a bare portion of specified length extending from the opposite end of the jacketed portion. The bare portion is spliced into the bare portion of another segment in the repeater""s optical circuit. Creating these splices can be a complicated task, requiring substantial lengths of bare fiber on each side of the splice. Optimally however, the repeater is designed to be as space-efficient as possible, thereby minimizing its production, storage, shipping, and installation costs. Thus, it is desirable to store each optical fiber segment in the most space-efficient manner possible.
FIG. 2 illustrates a perspective view of a known fiber storage device that can be located within, for example, a submarine optical repeater or branching unit. Tray 42 includes generally circular portal spool 44 which is surrounded by generally square portal well 48. The square portal well includes a fiber portal 68. Tray 42 also includes generally circular storage spool 46 which is surrounded by generally square storage well 50. Optical device 54 is mounted to tray 42 in optical cavity 52 which is connected to storage well 50 by cavity-to-storage channel 58 and by storage-to-cavity channel 64. Optical cavity 52 is connected to portal well 58 by portal-to-cavity channel 72 and cavity-to-portal channel 66.
Optical device 54 is connected to jacketed storage fiber 56 at the end of optical device 54 nearest storage well 50. Just inside storage well 50, jacketed storage fiber 56 connects to bare storage fiber 59. The end of bare storage fiber 59 is spliced to the end of bare connecting fiber 60 at splice 74. Bare connecting fiber 60 extends from splice 74 to jacketed connecting fiber 62 which, in turn, extends through storage-to-cavity channel 64, through optical cavity 52, through device-to-portal cavity 66, and into portal well 48. Within portal well 48, jacketed connecting fiber 62 wraps around portal spool 44 and exits at portal 68.
Jacketed connecting fiber 70 exits from the opposite end of optical device 54 and extends through portal-to-cavity channel 72, and into portal well 48, where it wraps around portal spool 44 and exits at portal 68. Spools 44 and 46 are designed with a radius greater than or equal to the reliability-adjusted minimum bending radius of the bare portion of fibers 56 and 60.
Although not shown, tray 42 can define more than one optical cavity and accompanying channels. In that situation, each additional optical fiber of any additionally mounted optical devices is routed and stored similarly to fibers 56, 59, 60, 62, and 70, i.e., in the channels connected to their respective optical cavity and around their respective spools. When more than one fiber is to be spooled around either spool 44 or 46, each additional fiber is wrapped around the spool generally above the preceding fibers, thereby forming a stack of spooled fibers.
Absent a late-stage design modification, jacketed fibers are generally not allowed to substantially intrude into the well where bare fiber is spooled, because such an intrusion can cause a jacketed fiber to press against or be spooled with a bare fiber. This is disadvantageous because the diameter of the jacketed fiber is much smaller than the reliability-adjusted minimum bending radius of the bare fiber. Thus, if the bare fiber is bent against the jacketed fiber, a violation of the minimum bending radius of the bare fiber can result, potentially causing unacceptable mechanical stresses in the bare fiber. Such a situation is particularly likely when a number of spooled bare fibers arc stacked on a spool, and each fiber must be pushed down into the well to make room for the successive fibers, the pushing action thereby greatly increasing the forces bending the bare fiber around the intruding jacketed fiber.
When intrusion is unavoidable, the jacketed portion may only extend into the well when the well has sufficient space to prevent the intruding jacketed portion from contacting the spooled bare portion. This means that the jacketed portion may typically intrude into the well by no more than about 1 inch. If the jacketed portion will intrude by more than about 1 inch, the tray design, or more typically the optical component design, should be modified to avoid damage to the bare fibers. However, when design changes substantially affect fiber portion lengths, other difficulties can ensue.
Changes in the length of the bare fiber portion can sometimes be accommodated by adjusting the amount of bare fiber wound around the spool, or adjusting how tightly the bare fiber is wound around the spool. However, an increase of more than 1 inch in the length of the jacketed fiber portion typically requires a chance to the optical component""s manufacturing specification, because, as discussed previously, such an increase could cause the jacketed fiber to intrude excessively into the bare fiber storage area. Likewise, a decrease in the jacketed fiber""s length could cause the bare fiber to be stored, unprotected, in a fiber channel, where it could be scratched by contact with the channel, or could be bent against an edge of the channel or another jacketed fiber.
As previously discussed, these types of situations could expose the bare fiber, and potentially the entire submarine optical fiber cable system, to unacceptable damage. Thus, changes in the length of the jacketed fiber portion often require a change to the optical component""s manufacturing specification. Such specification changes are typically very costly, particularly if initiated after the manufacturer has begun producing the optical component.
Thus, there is a need for a device that allows jacketed fiber and bare fiber to be stored in a protective, space-efficient, and separate manner, and that accommodates substantial changes to the length of jacketed fiber after the storage tray has been designed, and particularly after optical components have been specified and ordered.
Embodiments of the present invention provide a device for separating a first fiber portion from a second fiber portion of a fiber. The device can include a separator that can define at least one inner bearing surface adapted to restrain the first fiber portion from straightening when coiled within the separator. The separator can also define at least one outer bearing surface that can be adapted to limit a path defined by the second fiber portion when coiled on the separator. The path can vary with a longitudinal tension in the second fiber portion. The path can have a plurality of curves each having a radius. The radius of each curve of the path can at least meet a reliability-adjusted minimum bending radius of the second fiber portion. The separator can also define at least one separator opening adapted for passing the fiber therethrough.